In recent years, a secondary battery, which can be charged and discharged, has been widely used as an energy source for wireless mobile devices. In addition, the secondary battery has attracted considerable attention as a power source for electric vehicles (EV), hybrid electric vehicles (HEV), and plug-in hybrid electric vehicles (Plug-in HEV), which have been developed to solve problems, such as air pollution, caused by existing gasoline and diesel vehicles using fossil fuels.
In addition, technology related to a power storage device that stores electric power and stably supplies the stored electric power to a power system when needed has been developed. The power storage device is a device that stores electric power when power demand is low and supplies the stored electric power in case of overload or emergency. The power storage device provides the effect of improving quality of electric power and energy efficiency. In particular, a market for a household power storage device and a middle-sized industrial or commercial power storage device has been rapidly expanding as the power storage devices are related to smart grid technology.
Meanwhile, for a battery module to provide output and capacity required by a predetermined apparatus or device, it is necessary for the battery module to be configured to have a structure in which a plurality of battery cells is electrically connected to each other in series or in parallel. In addition, it is necessary for the battery module to be configured to have a structure which is easily extendable and stable as the capacity of the battery module is increased.
On the other hand, it is necessary for a battery pack used in an electric bicycle, an electric vehicle, or a hybrid electric vehicle to have durability such that the battery pack does not malfunction in a highly humid condition, such as the rainy season, and in various environments when used for a long period of time.
Particularly for a battery management system (BMS) or a printed circuit board (PCB), circuits are disposed in a dense state and loading density of elements is very high due to a compact structure of the battery pack. In a case in which external foreign matter, especially moisture, is introduced into the BMS or the PCB, therefore, the circuits and the elements may be easily corroded.
In addition, in a case in which moisture is introduced into an electrically connected structure of the arranged battery cells, a short circuit may occur with the result that the battery pack may malfunction or the lifespan of the battery pack may be greatly reduced.
Therefore, there is a high necessity for technology that is capable of fundamentally solving the above problems.